Photoreflectance characterization of GaAs/AlAs quantum wells with (4 1 1)A super-flat interfaces grown by molecular beam epitaxy

GaAs/AlAs quantum wells (QWs) with effectively atomically flat heterointerfaces over a large area [“View the MathML source super-flat interfaces”] grown on View the MathML source GaAs substrates by molecular beam epitaxy were characterized by room-temperature photoreflectance (PR) measurements. A larger PR signal corresponding to an optical transition between the 1st electron and the first heavy-hole levels (e1–hh1) was observed for the View the MathML source QW with a well width (Lw) of View the MathML source compared to the QW simultaneously grown on a (100) GaAs substrate. However, spectral line width of the PR signal from the View the MathML source QW was comparable to that of the (100) QW. In contrast with this, larger and sharper PR signals of e2–hh2 and e3–hh3 transitions were observed for the View the MathML source QWs with View the MathML source. The spectral line width of the room-temperature PR signal of the en–hhn transition with higher quantum index (n) is more sensitive to the interface flatness comparing to the low-temperature photoluminescence line width of the GaAs/AlAs QW.